U.S. patent application number 13/651675 was filed with the patent office on 2013-11-14 for method for continuously preparing carboxylic acid ester.
This patent application is currently assigned to China Petrochemical Development Corporation, Taipei (Taiwan). The applicant listed for this patent is CHINA PETROCHEMICAL DEVELOPMENT CORPORATION. Invention is credited to Jih-Dar Hwang, Yung-Shun Kung, Yao-Ching Tsai.
Application Number | 20130303796 13/651675 |
Document ID | / |
Family ID | 49531927 |
Filed Date | 2013-11-14 |
United States Patent
Application |
20130303796 |
Kind Code |
A1 |
Hwang; Jih-Dar ; et
al. |
November 14, 2013 |
METHOD FOR CONTINUOUSLY PREPARING CARBOXYLIC ACID ESTER
Abstract
A method for continuously preparing a carboxylic acid ester is
disclosed. In the method of the present invention, a vertical
reactor is filled with a solid catalyst, a carboxylic acid and an
alcohol are introduced into a lower part of the vertical reactor,
esterification is performed to form an esterized mixture, the
esterized mixture is output from an upper part of the vertical
reactor, and distillation is performed to isolate the carboxylic
acid ester. The method of the present invention is simple, easily
controlled and environmental friendly, and has significantly high
conversion rate and selectivity.
Inventors: |
Hwang; Jih-Dar; (Taipei
City, TW) ; Kung; Yung-Shun; (Taipei City, TW)
; Tsai; Yao-Ching; (Taipei City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CHINA PETROCHEMICAL DEVELOPMENT CORPORATION |
Taipei City |
|
TW |
|
|
Assignee: |
China Petrochemical Development
Corporation, Taipei (Taiwan)
Taipei City
TW
|
Family ID: |
49531927 |
Appl. No.: |
13/651675 |
Filed: |
October 15, 2012 |
Current U.S.
Class: |
554/170 ;
560/103; 560/204; 560/205; 560/265; 560/98 |
Current CPC
Class: |
C07C 67/08 20130101;
C07C 67/08 20130101; C07C 67/08 20130101; C07C 67/08 20130101; C07C
69/007 20130101; C07C 67/08 20130101; C07C 67/08 20130101; C07C
67/08 20130101; C07C 67/08 20130101; C07C 67/08 20130101; C07C
69/44 20130101; C07C 69/24 20130101; C07C 69/50 20130101; C07C
69/54 20130101; C07C 69/60 20130101; C07C 69/14 20130101; C07C
69/78 20130101; C07C 69/40 20130101; C07C 69/42 20130101; C07C
69/80 20130101; C07C 67/08 20130101; C07C 67/08 20130101 |
Class at
Publication: |
554/170 ;
560/204; 560/265; 560/205; 560/103; 560/98 |
International
Class: |
C07C 67/03 20060101
C07C067/03 |
Foreign Application Data
Date |
Code |
Application Number |
May 9, 2012 |
TW |
101116476 |
Claims
1. A method for continuously preparing a carboxylic acid ester,
comprising the steps of: introducing a carboxylic acid and an
alcohol into a lower part of a vertical reactor to perform an
esterification for forming an esterized mixture, wherein the
vertical reactor is filled with a solid catalyst; and outputting
the esterized mixture from an upper part of the vertical
reactor.
2. The method of claim 1, further comprising the step of distilling
the esterized mixture output from the vertical reactor for
isolating the carboxylic acid ester and water.
3. The method of claim 1, wherein before introducing the carboxylic
acid and the alcohol, the carboxylic acid and the alcohol are
mixed.
4. The method of claim 3, wherein a weight ratio of the carboxylic
acid to the alcohol is in a range of from 1:1 to 1:10.
5. The method of claim 1, wherein the carboxylic acid and the
alcohol are introduced into the lower part of the vertical reactor
at a liquid hourly space velocity range of 1 to 18 hour.sup.-1.
6. The method of claim 1, wherein the esterification is performed
at a temperature in a range of from 110 to 190.degree. C.
7. The method of claim 1, wherein the carboxylic acid is an
aliphatic carboxylic acid having 2 to 18 carbon atoms or an
aromatic carboxylic acid having 7 to 10 carbon atoms.
8. The method of claim 1, wherein the alcohol is a linear alcohol
having 1 to 3 carbon atoms.
9. The method of claim 8, wherein the alcohol is methanol, ethanol
or n-propanol.
10. The method of claim 1, wherein the solid catalyst is an acidic
cation exchange resin.
11. The method of claim 1, wherein the carboxylic acid is a
monocarboxylic acid.
12. The method of claim 11, wherein the monocarboxylic acid is an
aliphatic carboxylic acid having 2 to 18 carbon atoms or an
aromatic carboxylic acid having 7 to 10 carbon atoms.
13. The method of claim 11, wherein a weight ratio of the
carboxylic acid to the alcohol is in a range of from 1:1 to
1:6.
14. The method of claim 11, wherein the carboxylic acid and the
alcohol are introduced into the lower part of the vertical reactor
at a liquid hourly space velocity range of 1 to 12 hour.sup.-1.
15. The method of claim 11, wherein before introducing the
carboxylic acid and the alcohol, the carboxylic acid and the
alcohol are mixed at a temperature ranging from 30 to 80.degree.
C.
16. The method of claim 11, wherein the esterification is performed
at a temperature in a range of from 110 to 190.degree. C.
17. The method of claim 1, wherein the carboxylic acid is a
dicarboxylic acid.
18. The method of claim 17, wherein the dicarboxylic acid is one
selected from the group consisting of a saturated aliphatic
carboxylic acid having 4 to 10 carbon atoms, an unsaturated
aliphatic carboxylic acid having 4 to 10 carbon atoms and an
aromatic carboxylic acid having 7 to 10 carbon atoms.
19. The method of claim 17, wherein a weight ratio of the
carboxylic acid to the alcohol is in a range of from 1:3 to
1:10.
20. The method of claim 17, wherein the carboxylic acid and the
alcohol are introduced into the lower part of the vertical reactor
at a liquid hourly space velocity range of 2 to 18 hour.sup.-1.
21. The method of claim 17, wherein before introducing the
carboxylic acid and the alcohol, the carboxylic acid and the
alcohol are mixed at a temperature ranging from 50 to 75.degree.
C.
22. The method of claim 17, wherein the esterification is performed
at a temperature in a range of from 120 to 190.degree. C.
23. The method of claim 1, wherein the carboxylic acid and the
alcohol are introduced in the same direction into the vertical
reactor.
Description
FIELD OF INVENTION
[0001] The present invention relates to methods for continuously
preparing carboxylic acid esters, and more particularly, to a
method for continuously preparing a carboxylic acid ester from an
esterification of a carboxylic acid and an alcohol.
BACKGROUND OF THE INVENTION
[0002] Carboxylic acid esters are important chemical products, and
have great solubility, fluidity, non-toxicity and photo-stability.
The carboxylic acid ester may be used as materials for organic
syntheses applicable to a plasticizer, a solvent, a tobacco, a
spice, an essence, a cosmetic, a medicine, a dye, a surfactant, a
rubber, a plastic, a polyester resin, an adhesive, an artificial
fiber or a thin film material.
[0003] A traditional carboxylic acid ester is formed from an
esterification of a carboxylic acid and an alcohol catalyzed by
heat or an acid. The esterification is mainly performed in a liquid
phase, and after the reaction, the product is neutralized by an
alkali, washed and dried to remove sulfuric acid and byproducts, so
as to obtain the carboxylic acid ester. Since the carboxylic acid
ester is formed from the esterification of the alcohol and the
carboxylic acid in the liquid phase, the esterification is limited
by the reversible equilibrium, the reaction is incomplete and thus
the conversion rate of the esterification is low. In order to
increase the conversion rate of the esterification, concentrated
sulfuric acid is commonly used as the catalyst for the
esterification. However, the concentrated sulfuric acid is a strong
oxidant and a strong dehydrating agent, and thus results in side
reactions such as sulfonation, oxidation, etherification or
carbonization, so as to adversely affect the recovery and quality
of the ester compound. Further, due to using the concentrated
sulfuric acid as the catalyst, the anti-corrosion equipment is
needed and increases the production cost. Moreover, after the
reaction, a lot of acidic waste liquid would impair
environment.
[0004] Currently, to increase the conversion rate of the
esterification, Chinese Patent No. 1332924C discloses an
esterification of an organic acid. The conversion rate of this
esterification is more than 95%, but has the concentrated sulfuric
acid as a catalyst. The acidic waste liquid would result in
corrosion to equipment and in environmental pollution. Therefore,
this method is not suitable for continuous productions in the
industry.
[0005] U.S. Pat. No. 5,536,856 discloses an esterification method
and a device for preparing a carboxylic acid ester. In this method,
an ionic resin having sulphonic acid groups and/or carboxylic acid
groups are used as a catalyst and stacked in a plurality of trays.
The esterification is performed at a predetermined pressure,
wherein the reaction of the alcohol vapor and the acid is performed
via the catalyst. This method consumes a lot of alcohol and
carboxylic acid, but the carboxylic acid cannot be completely
conversed. Therefore, the production cost is high in this
method.
[0006] Chinese Patent Application Publication No. 100457263C
discloses a method for preparing a catalyst of a hetero polyacid
and/or a hetero polyacid salt carried on an inorganic carrier. The
catalyst is used for preparing a low-carbon carboxylic acid ester.
The catalyst may reduce corrosion to equipment and environmental
pollution. However, the preparation of the catalyst is complicated,
the activity period of the catalyst is short, and the
esterification rate is less than 90%.
[0007] Chinese Patent Application Publication No. 100503043C
discloses an ionic liquid catalyst for an esterification, the
preparation method and the use thereof. The ionic liquid catalyst
has high reactivity and causes less environmental pollution.
However, the reaction retention time is about 2 to 12 hours, and
after the reaction, the ester compound is separated from the ionic
liquid catalyst by gravity sedimentation. Therefore, the
esterification and the purification of the ester product are
time-consuming.
[0008] Hence, the sulfuric acid is used as the catalyst increasing
the esterification rate, but causes corrosion to equipment and
environmental pollution in the prior art.
[0009] Accordingly, there is a need to develop a method for
continuously preparing a carboxylic acid ester with a high
esterification rate, high selectivity and simple purification.
SUMMARY OF THE INVENTION
[0010] This invention provides a method for continuously preparing
a carboxylic acid ester. In accordance with the present invention,
a vertical reactor is filled with a solid catalyst, a carboxylic
acid and an alcohol are introduced into a lower part of the
vertical reactor to perform esterification, and after an esterized
mixture is formed, the esterized mixture is distilled to isolate
the carboxylic acid ester. In the esterification of the present
invention, three phases of materials exist at the same time,
wherein the ester product, and produced water and unreacted alcohol
are gas, and the catalyst is a solid. In the esterification, the
produced water is immediately removed from the reactor in the gas
phase, so that the reaction is toward the ester product, and thus
the carboxylic acid and the alcohol can be completely reacted.
[0011] In the method of the present invention, the boiling point of
the alcohol is lower than that of water. In accordance with the
present invention, the carboxylic acid and the alcohol are
introduced in the same direction into the vertical reactor, such
that while the gas phase contacts the liquid phase reversely in
reactive distillation, the flooding prevention is achieve and the
amount of continuously operation area are increased. Thus, the
amount of the carboxylic acid and the alcohol introduced into the
vertical reactor are significantly increased. In comparison with
the prior art, the method of the present invention produces
significantly more carboxylic acid ester in the continuous
operation. The esterized mixture is output from an part of the
vertical reactor, and the esterized mixture is distilled to isolate
the ester product.
[0012] In accordance with present invention, the method for
continuously preparing a carboxylic acid ester only needs one step
esterification, and has a great conversion rate of the carboxylic
acid and great selectivity. Moreover, the purification of the
carboxylic acid ester is simple, and thus the method of the present
invention is suitable for the continuous operation in the
industry.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] In the prior art, the esterification of the carboxylic acid
and the alcohol is performed in a liquid phase, such that the
esterification is limited by the reversible equilibrium and the
reaction is incomplete. Therefore, the concentrated sulfuric acid
is used as the catalyst or multiple batches of esterification are
performed for increasing the conversion rate and selectivity of the
esterification.
[0014] The present invention provides a method for continuously
preparing a carboxylic acid ester. In the method of the present
invention, a vertical reactor is filled with a solid catalyst, a
carboxylic acid and an alcohol are introduced into a lower part of
the vertical reactor and pass through the solid catalyst by pumping
to perform an esterification, the esterized mixture is output from
an upper part of the vertical reactor after the esterification, and
the esterized mixture is distilled to isolate the carboxylic acid
ester. In the method of the present invention, the carboxylic acid
and the alcohol are introduced in the same direction into the
vertical reactor, or mixed in advance and then introduced into the
vertical reactor. In the preferred embodiment of the present
invention, the carboxylic acid and the alcohol are mixed, and then
introduced into the lower part of the vertical reactor.
[0015] In the method of the present invention, a weight ratio of
the carboxylic acid to the alcohol in the esterification is in a
range of from 1:1 to 1:10, and the carboxylic acid and the alcohol
are introduced into the lower part of the vertical reactor at a
liquid hourly space velocity (LHSV) range of 1 to 18 hour.sup.-1.
The esterification is performed at a temperature ranging from 110
to 190.degree. C. Then, the unreacted alcohol is recovered, the
produced water is removed, and the distillation is performed to
isolate the carboxylic acid ester.
[0016] In the present invention, the alcohol is a linear alcohol
having 1 to 3 carbon atoms such as methanol, ethanol or n-propanol.
In the esterification of the present invention, the catalyst is a
solid catalyst such as an acidic ionic exchange resin.
[0017] In accordance with the present invention, the carboxylic
acid may be a monocarboxylic acid and a dicarboxylic acid, wherein
the monocarboxylic acid is an aliphatic carboxylic acid having 2 to
18 carbon atoms or an aromatic carboxylic acid having 7 to 10
carbon atoms. For example, the aromatic carboxylic acid is benzoic
acid. In a preferred embodiment, the carboxylic acid is one
selected from the group consisting of acetic acid, propionic acid,
butanoic acid, pentanoic acid, hexanoic acid, hepatanoic acid,
n-octanoic acid, nonanoic acid, capric acid, lauric acid, myristic
acid, palmitic acid, stearic acid, methacrylic acid and benzoic
acid. In the present invention, the dicarboxylic acid is a
saturated aliphatic carboxylic acid having 4 to 10 carbon atoms, an
unsaturated aliphatic carboxylic acid having 4 to 10 carbon atoms
or an aromatic carboxylic acid having 7 to 10 carbon atoms. For
example, the dicarboxylic acid may be succinic acid, glutaric acid,
hexanedioic acid, azelaic acid, decanedioic acid, isophthalic acid,
p-phthalic acid, fumaric aicd, maleic anhydride or phthalic
acid.
[0018] In one embodiment of the present invention, the
monocarboxylic acid is used, and the weight ratio of the
monocarboxylic acid to the alcohol for the esterification is in a
range of from 1:1 to 1:6. The monocarboxylic acid and the alcohol
are mixed in advance at a temperature ranging from 30 to 80.degree.
C., and then introduced into the lower part of the vertical reactor
at a liquid hourly space velocity (LHSV) range of 1 to 12
hour.sup.-1. The esterification is performed at a temperature
ranging from 110 to 190.degree. C.
[0019] In another embodiment of the present invention, the
dicarboxylic acid is used, and the weight ratio of the dicarboxylic
acid to the alcohol is in a range of from 1:3 to 1:10. The
dicarboxylic acid and the alcohol are mixed in advance at a
temperature ranging from 50 to 75.degree. C., and then introduced
into the lower part of the vertical reactor at a liquid hourly
space velocity (LHSV) range of 2 to 18 hour.sup.-1. The
esterification is performed at a temperature ranging from 120 to
190.degree. C.
[0020] In the present invention, the esterification is simple, one
step esterification and easily controlled. Furthermore, the
esterification in the present invention has a high conversion rate
and high selectivity.
[0021] The present invention is illustrated by, but not limited to,
the following examples. A person skilled in the art can easily
conceive the other advantages and effects of the present
invention.
[0022] In the present invention, the ester product was analyzed by
a gas chromatography. The selectivity of the esterification was
calculated according to the following equation.
selectivity (mole %)=mole number of ester in the product/(mole
number of the introduced carboxylic acid-mole number of carboxylic
acid in the product)
[0023] In the method for continuously preparing a carboxylic acid
ester of the present invention, the vertical reactor was a
stainless steel tube having an inner diameter of 0.5 inch and a
length of 100 cm and having a heating sleeve, and was filled with
acidic cation exchange resin (AMBERLYST 70).
Method for Continuously Preparing a Monocarboxylic Acid Ester
Embodiment 1
[0024] Acetic acid and ethanol at a weight ratio of 1:2 or 1:3 were
mixed at 30.degree. C., and then introduced into the lower part of
the vertical reactor at a liquid hourly space velocity (LHSV) of 3
hour.sup.-1. The reaction was performed at 115.degree. C. The
esterized mixture was output from the upper part of the vertical
reactor, and collected to be analyzed by gas photography. The acid
value of the product was determined by titration, and the
conversion rate and the selectivity were analyzed. The results were
shown in Table 1.
Embodiments 2 and 3
[0025] The method was performed as Embodiment 1 except that the
carboxylic acid and the alcohol were mixed at 30.degree. C., and
the weight ratio of the carboxylic acid and the alcohol, the
introductions rate and the reaction temperatures were shown in
Table 1. The analysis results of the products were shown in Table
1.
Embodiments 4 to 10
[0026] The method was performed as Embodiment 1 except that the
carboxylic acid and the alcohol were mixed at 50.degree. C., and
the weight ratio of the carboxylic acid and the alcohol, the
introductions rate and the reaction temperatures were shown in
Table 1. The analysis results of the products were shown in Table
1.
TABLE-US-00001 TABLE 1 Wt. Conversion Embodiment Carboxylic acid
Alcohol Temp. ratio LHSV rate of acid selectivity Embodiment 1
Acetic acid Ethanol 115.degree. C. 1:2 3 hr.sup.-1 98.68% 100%
Acetic acid Ethanol 115.degree. C. 1:3 3 hr.sup.-1 99.22% 100%
Embodiment 2 Acetic acid 95% Ethanol 110.degree. C. 1:2 4.5
hr.sup.-1 98.18% 100% Acetic acid 95% Ethanol 110.degree. C. 1:3 6
hr.sup.-1 99.38% 100% Acetic acid 95% Ethanol 115.degree. C. 1:3 3
hr.sup.-1 98.58% 100% Acetic acid 95% Ethanol 115.degree. C. 1:3
4.5 hr.sup.-1 98.54% 100% Embodiment 3 Propionic acid Methanol
130.degree. C. 1:2 4.5 hr.sup.-1 99.13% 100% Propionic acid 95%
Ethanol 130.degree. C. 1:2 6 hr.sup.-1 99.18% 100% Embodiment 4
Methacrylic Methanol 145.degree. C. 1:4 6 hr.sup.-1 99.31% 100%
acid Methacrylic Ethanol 145.degree. C. 1:4 6 hr.sup.-1 99.23% 100%
acid Embodiment 5 Pentanoic acid Methanol 120.degree. C. 1:2 6
hr.sup.-1 99.44% 100% Pentanoic acid 95% Ethanol 145.degree. C. 1:3
6 hr.sup.-1 99.27% 100% Pentanoic acid n-Propanol 145.degree. C.
1:3 6 hr.sup.-1 99.16% 100% Embodiment 6 Hexanoic acid Methanol
145.degree. C. 1:3 6 hr.sup.-1 99.72% 100% Hexanoic acid Methanol
145.degree. C. 1:3 9 hr.sup.-1 99.57% 100% Hexanoic acid Methanol
145.degree. C. 1:3 12 hr.sup.-1 99.05% 100% Hexanoic acid 95%
Ethanol 145.degree. C. 1:3 6 hr.sup.-1 99.22% 100% Embodiment 7
Benzoic acid Methanol 120.degree. C. 1:4 6 hr.sup.-1 99.45% 100%
Benzoic acid Ethanol 120.degree. C. 1:4 6 hr.sup.-1 99.10% 100%
Embodiment 8 n-Caprylic acid Methanol 145.degree. C. 1:3 6
hr.sup.-1 99.68% 100% n-Caprylic acid Methanol 145.degree. C. 1:3 9
hr.sup.-1 99.54% 100% n-Caprylic acid 95% Ethanol 145.degree. C.
1:4 6 hr.sup.-1 99.13% 100% Embodiment 9 Lauric acid Methanol
145.degree. C. 1:2 3 hr.sup.-1 99.12% 100% Lauric acid n-Propanol
145.degree. C. 1:5 6 hr.sup.-1 99.15% 100% Embodiment Stearic acid
Methanol 145.degree. C. 1:5 6 hr.sup.-1 99.48% 100% 10 Stearic acid
Methanol 145.degree. C. 1:5 9 hr.sup.-1 99.23% 100% Stearic acid
95% Ethanol 145.degree. C. 1:5 6 hr.sup.-1 99.15% 100%
Method for Continuously Preparing a Dicarboxylic Acid Ester
Embodiment 11
[0027] Hexanedioic acid and methanol at a weight ratio of 1:5 were
mixed at 50.degree. C., and then introduced into the lower part of
the vertical reactor at a liquid hourly space velocity (LHSV) of 6
hour.sup.-1. The reaction was performed at 130 to 175.degree. C.,
as shown in Table 2. The reaction was performed at 115.degree. C..
The esterized mixture was output from the upper part of the
vertical reactor, and collected to be analyzed by gas photography.
The acid value of the product was determined by titration, and the
conversion rate and the selectivity were analyzed. The results were
shown in Table 2.
Embodiments 12 to 14
[0028] The method was performed as Embodiment 11 except that the
carboxylic acid and the alcohol were mixed at 50.degree. C., and
the weight ratio of the carboxylic acid and the alcohol, the
introductions rate and the reaction temperatures were shown in
Table 2. The analysis results of the products were shown in Table
2.
Embodiment 15
[0029] The method was performed as Embodiment 11, except that
various carboxylic acids and ethanol at a weight ratio of 1:5 were
respectively mixed, and the reaction was performed at 160.degree.
C.. The analysis results of the products were shown in Table 2.
Embodiment 16
[0030] Decanedioic acid and various alcohols at a respective weight
ratio of 1:5 were mixed respectively at 50.degree. C., and
introduced into the lower part of the vertical reactor at a liquid
hourly space velocity (LHSV) of 6 hour.sup.-1. The reaction
temperature was 160.degree. C. The analysis results of the products
were shown in Table 2.
Embodiment 17
[0031] Fumaric acid and ethanol at a weight ratio of 1:8 were
mixed, and introduced in to the vertical reactor at the rate shown
in Table 2. The reaction temperature was 145.degree. C. The
analysis results of the products were shown in Table 2.
Embodiment 18
[0032] Maleic anhydride and methanol at a weight ratio of 1:5 were
mixed at 50.degree. C., and introduced in to the vertical reactor
at the rate shown in Table 2. The reaction temperature was
145.degree. C. The analysis results of the products were shown in
Table 2.
Embodiment 19
[0033] Maleic anhydride and ethanol at a weight ratio of 1:5 were
mixed at 65.degree. C., and introduced in to the vertical reactor
at the rate shown in Table 2. The reaction temperature was
145.degree. C. The analysis results of the products were shown in
Table 2.
Embodiment 20
[0034] Phthalic acid and various alcohols at a respective ratio of
1:7 were respectively mixed at 55.degree. C., and introduced in to
the vertical reactor at a liquid hourly space velocity (LHSV) of 3
hour.sup.-1. The respective reaction temperature was shown Table 2.
The analysis results of the products were shown in Table 2.
TABLE-US-00002 TABLE 2 Carboxylic Wt. Conversion Embodiment acid
Alcohol Temp. ratio LHSV rate of acid selectivity Embodiment 11
Hexanedioic Methanol 130.degree. C. 1:5 6 hr.sup.-1 100% 99.00%
acid Hexanedioic Methanol 145.degree. C. 1:5 6 hr.sup.-1 100%
99.47% acid Hexanedioic Methanol 160.degree. C. 1:5 6 hr.sup.-1
100% 99.64% acid Hexanedioic Methanol 175.degree. C. 1:5 6
hr.sup.-1 100% 99.59% acid Embodiment 12 Hexanedioic Methanol
145.degree. C. 1:5 9 hr.sup.-1 100% 99.32% acid Hexanedioic
Methanol 145.degree. C. 1:5 12 hr.sup.-1 100% 99.25% acid
Hexanedioic Methanol 160.degree. C. 1:5 12 hr.sup.-1 100% 99.33%
acid Hexanedioic Methanol 160.degree. C. 1:5 15 hr.sup.-1 100%
99.05% acid Hexanedioic Methanol 175.degree. C. 1:5 15 hr.sup.-1
100% 99.18% acid Hexanedioic Methanol 175.degree. C. 1:5 18
hr.sup.-1 100% 98.82% acid Embodiment 13 Glutaric acid Methanol
145.degree. C. 1:5 6 hr.sup.-1 100% 98.87% Glutaric acid Methanol
160.degree. C. 1:5 6 hr.sup.-1 100% 99.67% Embodiment 14 Succinic
Methanol 145.degree. C. 1:5 6 hr.sup.-1 100% 99.59% acid Succinic
Methanol 160.degree. C. 1:5 6 hr.sup.-1 100% 99.67% acid Embodiment
15 Hexanedioic Ethanol 160.degree. C. 1:5 6 hr.sup.-1 100% 99.03%
acid Glutaric acid Ethanol 160.degree. C. 1:5 6 hr.sup.-1 100%
99.02% Succinic Ethanol 160.degree. C. 1:5 6 hr.sup.-1 100% 99.18%
acid Embodiment 16 decanedioic Methanol 160.degree. C. 1:5 6
hr.sup.-1 100% 99.13% acid decanedioic Ethanol 160.degree. C. 1:5 6
hr.sup.-1 100% 98.34% acid Embodiment 17 Fumaric acid Ethanol
145.degree. C. 1:8 3 hr.sup.-1 100% 99.34% Fumaric acid Ethanol
145.degree. C. 1:8 6 hr.sup.-1 100% 99.26% Embodiment 18 Maleic
Methanol 145.degree. C. 1:5 6 hr.sup.-1 96.41% 100% anhydride
Maleic Methanol 145.degree. C. 1:5 9 hr.sup.-1 96.92% 100%
anhydride Embodiment 19 Maleic Ethanol 145.degree. C. 1:5 9
hr.sup.-1 96.76% 100% anhydride Maleic Ethanol 145.degree. C. 1:5
12 hr.sup.-1 96.24% 100% anhydride Embodiment 20 Phthalic acid
Methanol 120.degree. C. 1:7 3 hr.sup.-1 100% 99.31% Phthalic acid
n-Propanol 145.degree. C. 1:7 3 hr.sup.-1 100% 98.39%
[0035] Accordingly, the method for continuously preparing a
carboxylic acid ester of the present invention has short the
reaction time without using concentrated sulfuric acid as a
catalyst, so as to prevent the limitation of the reversible
equilibrium in the liquid phase, and thus to improve the conversion
rate of the carboxylic acid and the alcohol and the selectivity of
the ester. Moreover, the carboxylic acid ester is easily isolated
from the product, and the production efficacy is thus
increased.
[0036] The invention has been described using exemplary preferred
embodiments. However, it is to be understood that the scope of the
invention is not limited to the disclosed arrangements. The scope
of the claims, therefore, should be accorded the broadest
interpretation, so as to encompass all such modifications and
similar arrangements.
* * * * *